450 desmo carb

[Dan C]

Hi Bill,

Yes I feel for you too, that's a real bummer.

I agree with everything Duccout says. It does seem a bit weird that it wouldn't run with the Mk1 body. But it does tend to indicate that carburetion is the issue because every time you change something on the carb, there are changes to the way the bike runs.

But always difficult to know whether its ignition or carb and so his suggestion to borrow a carb if you can is wise. Someone in this forum suggested I do that (Jordan I think), but I wasn't able to do so as no suitable carb within miles.

Cheers
Dan

[Duccout]

That is one of the reasons why I recently fitted the Electrex World ignition system to my bike; I had low-down running problems and did not know if the cause was ignition or carburretion, so as the ignition system was old and messy, I fitted a new one to eliminate one possibility. Mind you, I think that I am still going to need a new carb!

[Jon Pegler]

Mark 1 Concentric carbs are generally simple, trouble free instruments.
One thing I don't like is the pressed in pilot jet.
I've come across a number of these carbs where a motor will not tick over and the problem is often that pressed in jet.
I put the carb on a pillar drill, mounting flange down, and run a long shank 1/8th inch drill down through the blanking plug at the inlet end, through the pressed in jet and down as far as the pilot air screw.
I then re-plug the hole at the inlet end and fit a screw in pilot jet inside the float chamber.
It usually cures the problem.

Jon

[themoudie]

Thank you Dan, Colin and Jon,

Jon, I too do not like the embeded pilot jet! I have also been on the Burlen website, again, and used the 'Vehicle Search'. Rather than using the 'Ducati' selection that displays the 750GT carb specification, I selected the 'DucatiMotrans' selection. This displays a range of the Spanish models and the result that interested me was the 'Road' one at the bottom of the list. The following information is for the 350 model:

Ducati Mototrans Road 350cc 1973 to 1974 930/417
Carburettor Specification: 930/417
Make: Ducati Mototrans
Model: Road
Engine Size: 350cc
Carb Type: Spanish MK I
Year: 1973 to 1974
Number of Carbs: 1
Needle Position: 2
Main Jet size: 220
Needle Jet size: Link does not work!?
Pilot Jet size: 30cc
Throttle Slide cutaway: 3½

I am sure that I read that the embedded pilot jet in the carbs intended for 4 strokes was only a 20cc size. So this could be the cause of some of my woes.

So, to drill or not to drill?

If were to buy a new 'Premier' 932 then the new replaceable pilot jet would be standard. But how does the No.15 - 23 'Premier' Pilot Jet equate to the previous cc flow rate range of pilot jets?

Questions for Burlen on Monday morning.

Good health, Bill

[Duccout]

What is the difference between the 'Premier' and 'Standard' carbs?

[Jordan]

Amal settings list shows the 930/417 to have needle jet = 106

[Bevel bob]

I feel your pain Bill. Been there. for years I put up with similar issues with my 250 and SSI carb. Eventually found a remote float (brand new) and fitted it. the new Needle seating and ability to adjust the fuel level at a whim sorted all my issues . Now it starts first kick, ticks over (mostly!) and does not cut out when the bike leans to one side. If only my joints were that easy to fix.

[themoudie]

Thank you all for your new comments.

Colin, you just need to go and have a read at this link: Burlen_Amal_carbs this may clear or muddy the waters further for you, but all the info is there.

Jordan, thank you, I went and dug out the Amal catalogue that they were handing out at Stafford 2019 and found it in the printed Applications table under Ducati Motrans. This is the size that I am using already and appears 'standard' for the 350-450 engine.

Aye Bob, that would make your eyes water! The last price shown for a complete SS1 float bowl on the Eurocarb web site is £198-50 and they are no longer available. Link: SS1-remote-float-bowl

I think that I will have a dry run with a 3mm drill up the pilot jet jacksie of one of the scrap Commando bodies that I have at my disposal, as Jon described in his last post. Then I may have a go at the body with the good fit for the slide that did nothing yesterday!

My regards, Bill

[Bevel bob]

Hi Bill, I bought an SS2 remote for £50 ,cheap as its too big for most, then swapped it with a USA member for anSS1.

[blethermaskite]

Bill, sorry for delay in reply, I use a variety of different length studs to accommodate the different thickness's of tufnol spacers, I wouldn't keep screwing cap heads into the head, the threads would just fail, sorry you are having so much trouble with the 450, I have never owned a 450 so my knowledge is limited on that engine capacity, however before you changed to the "better" mk1 body the dodgy starting and coldish running behaviour I still think is due to no choke. I have run various Ducati single over the years and like you didn't need a choke just a good flood with the tickler, but I have found more recently that with whatever that stuff is they now sell us as petrol its not that good on a Ducati single's cold starting without the ch
oke, personally on my own various 250s and 350s I have not had a problem with the sealed in pilot jet.......but then you are on a 450 so?????
I don't really know why because quite a lot of folk have fitted Mikuni carbs to a Ducati but I havn't and I have never had a Ducati through my hands that had been fitted with one so can't really help on that front either keep the faith you will get the gremlin eventually.
Cheers,
George